Catalysis of nickel nanodomains on Li-F dissociation for high-capacity fluoride cathodes with prior delithiation ability

Abstract

Transition metal fluoride is being considered as one of the most promising cathode materials due to its feasibility of high-voltage conversion reaction and high theoretical capacity. But the low solubility of LiF in fluoride is prone to degrade the electrode conductivity and Li-resource supply from fluoride cathode side, therefore limiting the reversibility of conversion reaction and its practical use in Li-ion batteries. Here, we propose a catalysis effect of Ni nanodomains to activate the Li-F splitting with much lower dissociation energy and to enable the LiF/Fe/Ni ternary cathode with superior conversion reaction capacity (600 mAh g−1) and rate performance (306 mAh g−1 at 3.8 A g−1). The crowded effect between LiF and dual-metal phases suppresses the growth of crystal grains and promotes the enrichment and penetration of LiF-Fe-Ni triple-phase interfaces. This compact interface contact endows the lithiated fluoride with an ultrahigh initial charge capacity exceeding 600 mAh g−1 and lowered charge plateau below 3.5 V. The preservation of interconnectivity and catalytic activity of electron conductive network enables the high reversibility of LiF splitting/recombination under high energy efficiency of 76%, as well as the electrochemical synthesis of rutile-like NixFe1−xF2 solid-solution phase. This fluoride cathode enables a release of high energy density (1414 Wh kg−1) under a power density of 849 W kg−1 and the energy density can still be preserved at 629 Wh kg−1 under an extremely high power densities of 3374 W kg−1. This work paves the way to develop the high-energy-density fluoride cathodes with the prior delithiation ability, which can lessen and even eliminate the use of Li metal at anode side.